Automatic choke



Nov. 7, 1961 M. F. STERNER ET AL 3,007,632

AUTOMATIC CHOKE Filed Feb. 29, 1960 INVENTORS MELVIN F. STERN ER MARION L. SMITLEY BY ARTHUR P.ZASKE ATTORNEYS s irk Patented Nov. '7, 1961 3,7,632 AUTUMA'HC CHGKE Melvin F. Sterner, Bloomfield Hills, Marion L. Smitley, Huntington Woods, and Arthur P. Zaslre, Utica, Mich, assignors to Holley Carburetor Company, Van Dylre, Mich, a corporation of Michigan Filed Feb. 29, 196i), Ser. No. 11,810 14 Claims, (ill. Z61--39) This invention relates to carburetors for internal cornbustion engines and refers more specifically to improved means for automatically operating the choking mecha nism within the carburetor.

Most carburetors of present design including automatic choking mechanism employ a coil type thermostatic bimetal for controlling the amount of choke opening according to temperature. They also use a manifold vacuum responsive piston for initially opening the choke a predetermined degree when the cold engine starts and becomes self sustaining. These pistons use vacuum bypass means, such as slots or ports which are fully opened or fully closed by a very small change of position of the piston, in order to control the extent of their movement.

Such systems have proved to be unsatisfactory because even though the amount of vacuum acting on the piston has been substantially reduced by the open bypass means there remains during further movement of the piston a sufficient degree of vacuum enabling the piston to exert a continual torque against the force of the bimetal, thereby seriously atfecting the proper functioning of the choke valve.

Another deficiency of such systems is that no means are provided for decreasing the time it takes for the bimetal thermostat to reach an equilibrium condition on further movement of the piston after it has reached a position opening the bypass means.

It is therefore one of the purposes of the present invention to provide improved means for rapidly reducing the torque of a choke vacuum piston to a minimum once its function has been performed.

Another purpose is to provide means for decreasing the time it takes for a bimetal thermostat of an automatic choke structure to reach an equilibrium condition on movement of the choke vacuum piston after it has reached a position opening piston bypass means.

More specifically it is a purpose of the present invention to provide a choke vacuum piston with a. valve responsive to engine vacuum, choke bimetal thermostat and choke plate unbalance which valve is operable to reduce the torque of a choke vacuum piston after a warm up period and to increase the flow of heated air around the choke bimetal thermostat after said warm up period.

Still more specifically it is an object to provide a choke vacuum piston including a valve therein having a sealing member movable to an unsealing position in an axial through opening in said piston in response to engine vacuum and choke plate unbalance in opposition to choke bimetal thermostat forces to reduce the effect of the vacuum piston on the choke operation to a minimum afiter a predetermined warm up period and to provide a passage for increased flow of warm air over the bimetal thermostat thereby decreasing the time necessary for the bimetal thermostat to reach an equilibrium condition during engine Warm up.

Another object is to provide structure as set forth above wherein said axial through opening is tapered radially outwardly toward the vacuum side of the piston whereby as said sealing member is moved axially away from its sealing position progressively more air flow around said sealing member is permitted.

Other objects and features of the invention will become apparent as the description proceeds, especially when taken in conjunction with the accompanying drawings, illustrating a preferred embodiment of the invention, wherein:

FIGURE 1 is a perspective view illustrating generally a carburetor including automatic choke means and embodying the invention.

FIGURE 2 is a fragmentary perspective exploded view illustrating the details of construction of the automatic choke mechanism shown on the left in FIGURE 1.

FIGURE 3 is a sectional view of a manifold vacuum responsive automatic choke piston according to the invention.

FIGURE 4 is a partial section view similar to FIGURE 3 of a modified vacuum responsive automatic choke piston according to the invention.

Referring to the drawings in greater detail, FIGURE 1 illustrates a carburetor ill having a throttle body 12 adapted to be mounted on an engine adjacent the induction manifold 13 thereof, an air intake 14 with induction passages therethrough adapted to be influenced by a choke valve 16, which is operatively connected by means of arms 18 and 2t? and link 22 to the automatic choke control 24.

FIGURE 2 illustrates a housing 26, suitably secured as by screws 23 to the carburetor it), having a cylinder 30 formed therein containing a piston 32 which is connected through a linkage 34 to the choke lever 36. A shaft 38, extending through and rotatable in one wall of the housing 26, has secured to it at one end thereof the choke lever 36 and at its other end secured to it lever 28 (FIGURE 1). The choke lever 36 has an outwardly extending projection 44) which is adapted to ccact with the free end 42 of thermostatic element 44- through an arcuate opening 46 in the housing cover plate 48.

The thermostatic housing 50 has a shaft located centrally within and rigidly secured to it to anchor the other end of the thermostatic element 44. Any suitable means such as the clamping ring 52 may be employed to hold the cover plate 48 and housing Si) in alignment with and against the housing 26. The ring 52 may be secured by means of screws 54 and cooperating threaded portions 56.

Conduit 58 communicates between a source of heated air as for example the exhaust manifold 59 and the chamber formed generally by cover plate 53 and housing 50. As shown diagrammatically in FIGURE 3 a stove portion 61 comprising housing rs and coiled conduit 65 adapted to receive fresh air to be heated as it passes through the conduit 65 is provided in the exhaust manifold 59. The purpose of conduit 58 is to deliver air, which is at a temperature indicative of engine temperature, to the thermostatic element 44 in order that the element may react to it and change the position of the choke valve 16 accordingly.

Conduit 66' (FIGURE 1) communicates generally between the cylinder ?A) and a source of engine manifold vacuum in such a manner so as to draw air through conduit 5S and cause movement of the piston 32 in a direction so as to result in clockwise rotation of lever 36.

FIGURE 3 illustrates in greater detail, the details of the choke vacuum piston 32 and cylinder 30. The piston is connected to a linkage 34 through ball valve means 62; the opposite end of the link 34- is opcratively connected to lever 36 by means of pin 64 which is retianed within lever 36 and slidable within the 10st motion producing slot 66 of link As shown in FIGURE 3 the right or outer end of cylinder 39 is closed by a removable cap '70 to permit insertion of stop 72 within grooves 74 provided on the interior surface of the cylinder for this purpose. Grooves '74 do not act as piston bypass passages. It will be noted that stop 72 includes radially inwardly extending portion o 76 operable to limit rightward travel of piston 32 in cylinder 3t).

Piston 32 as illustrated is provided with an axial through passage '73. Passage 78 includes radially inwardly projecting flange St? having a valve seat 32 on the right or vacuum side thereof adapted to receive sealing member 62. Passage 78 further includes the portion 84 radially enlarged with respect to sealing member 62 and the radially outwardly tapering portion 86 adapted to permit progressively large amounts of air to flow through piston 32 as the sealing member moves further away from valve seat 32 in operation of the automatic choke as will be seen.

In considering the operation of the invention it will be assumed, for the purpose of illustration, that the engine is cold and is being cranked, the thermostatic element 44 will be in its unwound condition thereby causing its end 42 to position projection 44 of lever 36 in its extreme counter-clockwise position. The lever 36 being secured to shaft 38 rotates the shaft and arm 20, which is secured to it, counterclockwise thereby causing the choke valve to assume a position which substantially closes cit the flow of air through the carburetor induction passage. All of these elements will continue to occupy these respective positions while the engine is being cranked.

As soon as the engine fires and becomes self-sustaining, manifold vacuum rises to a value sufiicient to move the vacuum piston toward the closed end of the cylinder against the projection 76 of stop 72 to the broken line position shown in FIGURE 3 in opposition to the force of thermostat 44. This may be accomplished by means of suitable conduitry which causes the open end of piston 30 to be subjected to substantially atmospheric pressure while the closed end of the piston is subjected to manifold vacuum through conduit 60. As the engine continues to run, air is drawn from a suitable stove through conduits 58 and $8, through an orifice 92 in cover plate 48, into the chamber formed by the housing 5t? and cover plate 48. The air then warms the thermostat 44 and passes into the chamber formed by housing 26 and cover plate 48 through the arcuate opening 46 within the cover plate. The air is then drawn past the piston 32 due to sliding clearance provided for piston 32 into passage 90, which leads from the cylinder 30 to conduit 6d which is connected to a source of manifold vacuum. A small opening 93 serving as a direct hot air bypass may also be included if desired.

At this time the ball valve sealing member 62 is firmly held in sealed position against valve seat 82 since the counter-clockwise force exerted by the bimetal thermostat 44 is greater than the clockwise force exerted on sealing member 62 due to choke plate unbalance and manifold vacuum. After a predetermined warm up time the bi metaal thermostat rotates due to heating to a position to permit moving of ball valve sealing member 62 away from valve seat 82.

According to the invention since the through opening is tapered as at 86 the air flow past sealing member 62 as it moves away from seat 82 toward the position shown at 62" from that indicated at 62' becomes progressively larger. Thus the effect of manifold vacuum on piston 32 will be reduced to a minimum on movement of sealing member 62 away from seat 82. Furthermore, increased hot air flow around sealing member 62 and bimetal thermostat 44 due to the tapered portion 8 5 of passage 78 the time necessary for the bimetal thermostat 44 to reach a fully clockwise position after sealing member 62 starts moving away from seat 82 will be decreased as desired.

A slightly modified form of the improved automatic choke of the invention is illustrated in FIGURE 4. In the modification of FIGURE 4 the stop 72 having projection 76 which is fixed axially of cylinder 30 as shown in FIGURE 3 is replaced by the screw 94 having a conical end surface 96. The end surface 96 serves as an adjustable stop for piston 32 since as the screw 94 is adjusted radially with respect to cylinder 30 the piston 32 contacts the conical surface 9-5 when the piston is in different positions axial of the cylinder.

In this manner the initial axial position of piston 32 in cylinder 3t) on creating a vacuum in cylinder 3% may be adjusted with the invention modified as shown in FiG- URE 4- to re ulate the force with which sealing member 62 is held against seat 82. Thus the temperature at which the bimetal thermostat will cause the member 62 to move away from seat 82 and therefore the time required for unseating the sealing member 62 may be regulated.

T he drawings and the foregoing specification constitute a description of the improved automatic choke in such full, clear, concise and exact terms as to enable any person skilled in the art to practice the invention, the scope of which is indicated by the appended claims.

What we claim as our invention is:

1. In a carburetor, a choke valve, a source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means communicating with the source of vacuum operatively connected to said choke valve, and a separate valve member distinct from said pressure responsive means responsive to said temperature responsive means, said pressure responsive means and choke valve unbalance operable to reduce the eifect of the pressure responsive means on said choke valve to a minimum after said temperature responsive means passes a predetermined temperature.

2. Structure as claimed in claim 1 wherein said temperature responsive means comprises a thermostatic bi metal coil and including lever and connecting link means operably securing one end of said thermostatic bi-metal coil to said choke valve and means fixedly holding the other end of the bi-metal coil relative to said choke valve.

3. In a carburetor, a choke valve, a source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means comprising a vacuum responsive piston communicating with the source of vacuum operatively connected to said choke valve, and valve means extending through said piston responsive to said temperature responsive means, said pressure responsive means and choke valve unbalance operable to reduce the effect of the pressure responsive means on said choke valve to a minimum after said temperature responsive means passes a predetermined temperature.

4. Structure as claimed in claim 3 wherein said valve means comprises a through opening in said piston having a valve seat therein and a movable valve member positioned within said through opening, said movable valve member being operable in response to said temperature responsive means, said pressure responsive means, and said choke valve unbalance to move within said through opening between a fully open position wherein said pressure responsive means is ineffective to control said choke valve and a sealing position on said valve seat.

5. Structure as claimed in claim 4 wherein said through opening is tapered from said valve seat radially outwardly toward the vacuum side of said piston to provide for a progressively larger air flow around said valve member and temperature responsive means as said valve member is moved away from said valve seat to decrease the time necessary for the temperature responsive means to reach an equilibrium condition.

6. Structure as claimed in claim 4 wherein said through opening includes an enlarged portion adjacent said valve seat on the vacuum side of the piston and tapers radially outwardly from said enlarged portion.

7. Structure as claimed in claim 3 including an adjustable stop operable to limit the axial movement of said piston in one direction within said piston.

8. Structure as claimed in claim 7 wherein said adjustable stop comprises a screw having a conical end adjustably secured in a wall of said cylinder whereby on adjustment of said screw said conical end moves radially into and out of said cylinder.

9. In a carburetor operatively associated with an engine, a choke valve, a source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means communicating with the source of vacuum operatively connected to said choke valve, and a separate valve member distinct from said pressure responslve means responsive to said temperature responsive means, said pressure responsive mean and choke valve unbalance operable to reduce the eiTect of the pressure responsive means on said choke valve to a minimum after said temperature responsive means passes a predetermined temperature, said choke plate unbalance having maximum effect on said valve means at higher engine speeds.

10. In a carburetor, a choke valve, 21 source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means communicating with the source of vacuum operatively connected to said choke valve, and a separate valve member distinct from said pressure responsive means responsive to said tem perature responsive means, said pressure responsive means and choke valve unbalance operable to increase by pro gressively larger amounts the effect of the temperature responsive means on said choke valve to a maximum after said temperature responsive means passes a predetermined temperature.

li. In a carburetor, a choke valve, a source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means comprising a cylinder having a closed end connected to the source of vacuum, a piston reciprocal Within said cylinder, and valve means extending through said piston including a movable valve member, and lever and connecting link means operably connecting said pressure responsive means to said choke valve, said valve means being responsive to said temperature responsive means, said pressure responsive means and choke valve unbalance to reduce the effect of the pressure responsive means on said choke valve to a minimum after said temperature responsive means passes a predetermined temperature.

12. In a carburetor, a choke valve, a source of vacuum, temperature responsive means influencing the position of the choke valve, pressure responsive means communicating with the source of vacuum operatively connected to said choke valve, and separate valve means positioned radially and axially centrally of said pressure responsive means responsive to said temperature responsive means, said pressure responsive means and choke valve unbalance operable to reduce the effect of the pressure responsive means on said choke valve to a minimum after said temperature responsive means passes a predetermined temperature.

13. A valve, a source of vacuum, temperature responsive means influencing the position of the valve, pressure responsive means communicating with the source of vacuum operatively connected to said valve, and a separate valve member distinct from said pressure responsive means responsive to said temperature responsive means, said pressure responsive means being operable to reduce the effect of the pressure responsive means on said valve to a minimum after said temperature responsive means passes a predetermined temperature.

14. A valve, a source of vacuum, temperature responsive means influencing the position of the valve, pressure responsive means communicating with the source of vacuum operatively connected to said valve, and separate valve means positioned radially and axially centrally of said pressure responsive means responsive to said temperature responsive means, said pressure responsive means being operable to reduce the eitect or" the pressure responsive means on said valve to a minimum after said temperature responsive means passes a predetermined temperature.

References Cited in the file of this patent UNITED STATES PATENTS 

